We propose to create the Center for Bioelectric Field Modeling, Simulation, and Visualization within the NIH/NCRR Biomedical Research Technology Program. The need for such a Center lies in the broad and expanding use of computational tools in acquiring, analyzing, and interpreting bioelectric fields. These fields arise from all living organisms and are the physical basis for the discipline of electrophysiology and its clinical implementations, most notably in cardiology and neurology. With the widespread availability of computers for bioelectric field research has come a large demand for software that is specialized for the study of bioelectric phenomena. Compared to other areas of engineering, the pace of development of software for bioelectric field problems has been modest. The technology research and development component of the proposed Center consists of three topics: geometric modeling, numerical simulations, and scientific visualization. Within each topic are specific projects that include the development of novel methods, algorithms, and software for solving bioelectric field problems. This work will be carried out in close collaboration with six experts in a variety of areas in cardiac- and neuro-electrophysiology. Each collaboration contains specific projects that reflect the most pressing computation needs of these scientists. An essential integrating component of the proposed research is a uniform, portable problem-solving software environment that will permit seamless movement of data and application of computation modules. The end product of each of the research and collaborative projects will be software modules for this problem-solving environment. In some cases, the collaborators themselves will create the modules with the help of members of the Center: in other cases, the modules will come from the research and development of the Center. The potential impact of this research resource will extend throughout the electrophysiology research community but also to related disciplines in which scalar-valued fields are measured, analyzed, computer, or visualized. The software tools created by the Center will be made freely available to the scientific community and support in the form of documentation, web-site distribution, and educational seminars carried out by the Center.